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United States Patent |
5,155,787
|
Carpenter
,   et al.
|
October 13, 1992
|
Multiple optical fiber splice element having ramped porch
Abstract
A device for splicing multiple optical fibers includes a novel splice
element having two plates formed from a sheet of malleable material, there
being a fold line in the sheet forming a hinge, the two plates being
folded toward one another to define opposing surfaces. One of the opposing
surfaces has several fiber receiving grooves therein, parallel with the
fold line, and the other surface has ramps at each end to support the
fibers proximate the transition from their buffered portions to their
stripped portions. The ramps are adjacent porches which are integrally
formed with one of the plates, the porches having additional grooves for
aligning the fibers with the fiber receiving grooves. Stop pads are
provided on both opposing surfaces, at the corners of the plates, to
insure a clearance space at the ends of the plates which provides for more
gradual clamping of the fibers, reducing insertion loss.
Inventors:
|
Carpenter; James B. (Austin, TX);
Larson; Donald K. (Cedar Park, TX);
Mansfield; Charles M. (Austin, TX);
Patterson; Richard A. (Georgetown, TX)
|
Assignee:
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Minnesota Mining and Manufacturing Company (St. Paul, MN)
|
Appl. No.:
|
753333 |
Filed:
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September 6, 1991 |
Current U.S. Class: |
385/98; 385/71; 385/137 |
Intern'l Class: |
G02B 006/38 |
Field of Search: |
385/65,70,71,83,136,137,95,97,98
|
References Cited
U.S. Patent Documents
3864018 | Feb., 1975 | Miller | 350/96.
|
4028162 | Jun., 1977 | Cherin et al. | 156/158.
|
4029390 | Jun., 1977 | Chinnock et al. | 350/96.
|
4045121 | Aug., 1977 | Clark | 350/96.
|
4046454 | Sep., 1977 | Pugh, III | 350/96.
|
4102561 | Jul., 1978 | Hawk et al. | 350/96.
|
4181401 | Jan., 1980 | Jensen | 350/96.
|
4201443 | May., 1980 | Hodge | 350/96.
|
4203650 | May., 1980 | Millet et al. | 350/96.
|
4211470 | Jul., 1980 | Stewart | 350/96.
|
4220397 | Sep., 1980 | Benasutti | 350/96.
|
4254865 | Mar., 1981 | Pacey et al. | 206/316.
|
4257674 | Mar., 1981 | Griffin et al. | 350/96.
|
4258977 | Mar., 1981 | Lukas et al. | 350/96.
|
4274708 | Jun., 1981 | Cocito et al. | 350/96.
|
4300815 | Nov., 1981 | Malsot et al. | 350/96.
|
4325607 | Apr., 1982 | Carlsen | 350/96.
|
4352542 | Oct., 1982 | Tydings | 350/96.
|
4353620 | Oct., 1982 | Schultz | 350/96.
|
4354731 | Oct., 1982 | Mouissie | 350/96.
|
4391487 | Jul., 1983 | Melman et al. | 350/96.
|
4399172 | Jul., 1982 | Leather | 350/96.
|
4435038 | Mar., 1984 | Soes et al. | 350/96.
|
4470180 | Sep., 1984 | Blomgren | 24/563.
|
4593971 | Jun., 1986 | Clement et al. | 350/96.
|
4602845 | Jul., 1986 | Anderton | 350/96.
|
4634216 | Jan., 1987 | Calevo et al. | 350/96.
|
4730892 | Mar., 1988 | Anderson et al. | 350/96.
|
4740411 | Apr., 1988 | Mitch | 428/175.
|
4824197 | Apr., 1989 | Patterson | 385/98.
|
4865412 | Sep., 1989 | Patterson | 385/71.
|
4865413 | Sep., 1989 | Hubner et al. | 350/96.
|
4871227 | Oct., 1989 | Tilse | 350/96.
|
4930859 | Jun., 1990 | Hoffman, III | 350/96.
|
4940307 | Jul., 1990 | Aberson et al. | 350/96.
|
4973126 | Nov., 1990 | Degani et al. | 350/96.
|
5016970 | May., 1991 | Negase et al. | 350/96.
|
5037179 | Aug., 1991 | Bortolin et al. | 385/54.
|
Foreign Patent Documents |
82102571.5 | Dec., 1985 | EP.
| |
88303777.2 | Nov., 1988 | EP.
| |
52-19547 | Feb., 1977 | JP.
| |
53-26142 | Mar., 1978 | JP.
| |
58-9114 | Jan., 1983 | JP.
| |
58-158621 | Sep., 1983 | JP.
| |
Other References
Reliable Corelink.TM. Tomorrow's Fiber Optic Splice Today! Published by
Reliance Comm/Tec--Copyright date of 1991 By E. C. Scholtens, 5 pages.
|
Primary Examiner: Lee; John D.
Attorney, Agent or Firm: Griswold; Gary L., Kirn; Walter N., Musgrove; Jack V.
Claims
I claim:
1. An element for splicing a first plurality of optical fibers to a second
plurality of optical fibers, the element comprising:
first and second plate members forming a pair of opposing surfaces, at
least one of said opposing surfaces of said first and second plate members
having a plurality of fiber receiving grooves therein; and
first and second porch members attached to first and second ends,
respectively, of said first plate member, said first and second porch
members extending beyond first and second ends of said second plate
member, respectively, said first and second porch members having surfaces
which have guide grooves formed therein, said guide grooves being aligned
with said fiber receiving grooves but extending beyond said first and
second ends of said second plate member whereby the first plurality of
optical fibers may be laid onto said guide grooves in said first porch
prior to insertion of said first plurality of fibers in said fiber
receiving grooves, and the second plurality of optical fibers may be laid
onto said guide grooves in said second porch prior to insertion of said
second plurality of fibers in said fiber receiving grooves.
2. The element of claim 1 wherein said first and second plate members are
formed from a single sheet of malleable material having a fold line
therein forming a hinge.
3. The element of claim 1 wherein said opposing surfaces are formed of a
malleable material.
4. The element of claim 1 wherein said fiber receiving grooves are formed
in said opposing surface of said second plate member.
5. The element of claim 1 for use with fibers having a buffered portion and
an exposed portion, wherein said first and second ends of said first plate
member include ramp means for supporting the fibers proximate a transition
between the buffered and exposed portions of the fibers, said guide
grooves being adjacent said ramp means.
6. The element of claim 5 wherein the buffered portions of the fibers have
a buffer coating of known thickness, and:
said first and second porch members are integrally formed with said first
and second ends of said first plate member, respectively;
said guide grooves are recessed in said surfaces of said porch members; and
said ramp means comprises a ramped surface extending from said recessed
guide grooves to said opposing surface of said first plate member, said
ramped surface having a height which is approximately equal to the
thickness of the buffer coating.
7. The element of claim 1 wherein at least one of said first and second
plate members includes means providing a clearance space between said
opposing surfaces at said first and second ends of said first and second
plate members.
8. The element of claim 1 further comprising a third plate member adjacent
said second plate member, forming a second pair of opposing surfaces, at
least one of said surfaces in said second pair having a second plurality
of fiber receiving grooves therein.
9. An element for splicing a first plurality of optical fibers to a second
plurality of optical fibers, the element comprising:
first and second plate members forming a pair of opposing surfaces each
having first and second ends, at least one of said surfaces having a
plurality of fiber receiving grooves therein; and
clearance means for providing a space between said opposing surfaces at
said first and second ends thereof whereby, when said opposing surfaces
are clamped toward one another, a higher clamping force is applied at a
center of the element than at said first and second ends thereof.
10. The element of claim 9 wherein said space formed by said clearance
means further allows insertion of the pluralities of fibers between said
first an second plate members.
11. The element of claim 9 wherein said clearance means comprises a
plurality of pads attached to said opposing surface of said first plate
member at said first and second ends thereof.
12. The element of claim 11 wherein said first plate member has a generally
rectangular shape defining four corners, and said opposing surface of said
first plate member has four pads integrally formed thereon, one pad at
each of said corners.
13. The element of claim 9 intended for use with fibers having a buffered
portion, the element further including a porch area having ramp means for
receiving the buffered portion of the fibers, said ramp means including
guide grooves which are generally aligned with said fiber receiving
grooves.
14. The element of claim 9 further comprising a third plate member adjacent
said second plate member, forming a second pair of opposing surfaces, at
least one of said surfaces in said second pair having a second plurality
of fiber receiving grooves therein.
15. An element for splicing a first plurality of optical fibers to a second
plurality of optical fibers, the element comprising:
first and second plate members, defining a first pair of opposing surfaces,
both of said surfaces of said first pair being malleable and at least one
of said surfaces of said first pair having a first plurality of fiber
receiving grooves therein; and
a third plate member, said second and third plate members defining a second
pair of opposing surfaces, both of said surfaces of said second pair being
malleable and at least one of said surfaces of said second pair having a
second plurality of fiber receiving grooves therein, and at least two of
said first, second and third plate members being formed from a single
sheet of malleable material having a fold line forming a hinge.
16. The element of claim 15 further comprising means for guiding a first
set of the first plurality of optical fibers to said first plurality of
fiber receiving grooves and for guiding a second set of the first
plurality of optical fibers to said second plurality of fiber receiving
grooves.
17. The element of claim 16 wherein said guiding means comprises a plug
adjacent a first end of said first, second and third plate members, said
plug having a first set of orifices directed toward said first plurality
of fiber receiving grooves, and a second set of orifices directed toward
said second plurality of fiber receiving grooves.
18. The element of claim 15 wherein said first, second and third plate
members are all formed from a single sheet of malleable material, said
sheet having two fold lines forming hinges and being folded in a Z-shape.
19. The element of claim 15 wherein said first plate member has first and
second ends, and includes means providing a clearance space between said
first pair of opposing surfaces at said first and second ends.
20. An element for splicing a first plurality of optical fibers to a second
plurality of optical fibers, the element comprising:
a first generally rectangular plate having first and second ends, and four
corners, and further having ramped surfaces at said first and second ends;
first and second porches attached to and integral with said first and
second ends, respectively, of said first plate, said porches having a
plurality of recessed guide grooves immediately adjacent said ramped
surfaces;
a second generally rectangular plate approximately equal in size to said
first plate, said first and second plates being formed from a single sheet
of malleable material having a fold line forming a hinge, said first and
second plates being folded toward one another, defining an opposing
surface of said second plate, said opposing surface having a plurality of
fiber receiving grooves therein, aligned with said guide grooves in said
porches and generally parallel with said fold line; and
at least four pads integrally formed on said first plate, one pad at each
of said corners.
21. An element for splicing a first plurality of optical fibers to a second
plurality of optical fibers, each of the optical fibers having a buffered
portion and an exposed portion, the buffered portions having a buffer
coating of known thickness, the element comprising first and second plate
members forming a pair of opposing surfaces, at least one of said opposing
surfaces of said first and second plate members having a plurality of
fiber receiving grooves therein, said first plate member having first and
second ends, and first and second ramped surfaces formed on said first and
second ends, respectively, for supporting the fibers proximate a
transition between the buffered and exposed portions of the fibers, said
ramped surfaces having a height which is approximately equal to the
thickness of the buffer coating.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to devices for optically connecting
the ends of waveguides such as optical fibers, and more particularly to an
article which splices a plurality of pairs of such optical fibers.
2. Description of the Prior Art
Splice devices for optical fibers are known in the art, but there is still
a need for a quick and reliable method of splicing a plurality of fibers
in a high density environment. Prior to the introduction of splice devices
which join a plurality of optical fibers in a single splice body
(discussed further below), this was accomplished by utilizing a plurality
of single fiber (discrete) splice devices. This approach was very time
consuming, however, and further resulted in a large volume of splice
bodies which crowd junction boxes, or require specialized splice trays to
keep the fibers organized.
Several systems have been devised to address the problem of multiple fiber
splicing. One technique, mass fusion welding, requires that each fiber be
placed in a groove of a rigid substrate having several such grooves. Best
fit averaging is used to align the fiber pairs and an electric arc is
created, melting the fiber tips and permanently fusing them together. The
primary, and very significant, limitation of fusion splicing is the great
expense of the fusion welders. Fusion welding also precludes later fiber
removal or repositioning.
Another common multiple splicing technique requires the use of adhesives,
again with a substrate or tray that has a plurality of grooves therein.
For example, in U.S. Pat. No. 4,028,162, a plurality of fibers are first
aligned on a plastic substrate having fiber aligning grooves, and then a
cover plate is applied over the fibers and the substrate, the cover plate
having means to chemically adhere to the fiber and substrate. Adhesives
are also used in the optical fiber splice devices disclosed in U.S. Pat.
No. 4,029,390 and Japanese Patent Application (Kokai) No. 58-158621. The
use of adhesives is generally undesirable since it adds another step to
the splicing process, and may introduce contaminants to the fiber
interfaces. Splice devices using adhesives also require extensive
polishing of the fiber end faces to achieve acceptable light transmission,
and some adhesive splices further require the use of a vacuum unit to
remove trapped air.
The '390 patent represents an improvement over earlier multiple splice
devices in that it utilizes a foldable holder having a series of V-grooves
on both sides of a central hinge region. The method of attaching the
fibers to the holder, however, presents additional problems not present in
earlier splices. First of all, since adhesive is used to affix the fibers
to the holder before splicing, the cleaving of the fibers becomes a
critical step since the cleave length must be exact to avoid any offset of
the fiber end faces, which would be extremely detrimental to splice
performance. Secondly, it is critical that the opposing V-grooves be
exactly aligned, which is unlikely with the hinge depicted in the '390
patent; otherwise, there will be transverse fiber offset resulting in
increased signal loss. Finally, the '390 holder would not maintain the
opposing plates perfectly parallel, which is necessary in order to
optimize transverse alignment of the fiber pairs, and also affects fiber
deformation.
Another problem with several of the foregoing splicing devices is that they
used rigid substrates to clamp the fibers. There are several disadvantages
to the use of rigid substrates. First of all, it is generally more
difficult to form grooves in a rigid material, such as by etching,
grinding or erosion, which increases manufacturing cost. Rigid substrates
must also be handled more carefully since they are brittle and thus easily
damaged. Most importantly, the use of a rigid substrate having grooves
therein results in poor alignment of the fiber pairs (as well as
unnecessary fiber deformation), leading to higher insertion loss. These
problems are compounded in stacked configurations such as those shown in
U.S. Pat. Nos. 3,864,018, 4,046,454 and 4,865,413.
These difficulties may be avoided by the use of a substrate which is
malleable, elastomeric or ductile. Unfortunately, however, the use of such
materials has not been fully appreciated nor implemented. For example,
U.S. Pat. No. 4,046,454 teaches that the rigid V-grooves may be lined with
a ductile material. This complicates the manufacturing process, however,
and adds significant cost. In U.S. Pat. No. 4,102,561, the splice device
utilizes two alignment members formed of a resilient material which may
deform against the fiber surfaces. That splice, however, requires the
attachment of two subassemblies prior to insertion of the fibers into the
alignment members, and further uses about a dozen clamps and bolts, making
the device very difficult to use in the field (similar problems apply to
the device illustrated in U.S. Pat. No. 4,045,121). The primary clamping
action directly at the fiber interface also causes deformation of the
fiber resulting in more signal loss than if there were a more gradual
clamping toward the interface. This problem also applies to other splice
designs, such as that depicted in European Patent Application No.
88303777.2, which further suffers from the non-uniform application of
clamping forces to different fibers.
In light of the foregoing, it would be desirable and advantageous to devise
a high performance splice device for multiple optical fibers which does
not require fusion welding, or adhesives and polishing. The device should
provide a uniform clamping force to each of the fibers, and provide
gradual clamping to minimize undesirable deformations such as microbending
at the clamp transition. The cleave length of the fibers should not be
critical, and means should be provided to optimize fiber alignment,
including the use of malleable clamping surfaces. Finally, the splice
should be simple to use, especially for field installation.
SUMMARY OF THE INVENTION
The foregoing objectives are achieved in a device for splicing multiple
optical fibers comprising a splice element, a body surrounding the splice
element, and a wedge providing uniform, transverse clamping of the fibers
in the splice element. The body may be comprised of a jacket portion and a
cap portion which interlock to hold the splice element. The splice element
is preferably formed of a malleable material, and is hinged to define two
plates, one plate having a series of parallel V-grooves, and the plates
being folded together prior to actuation by the wedge. Stop pads are
interposed between the plates to insure gradual clamping when the wedge is
forcibly urged against the plates or against a tongue which is interposed
between the plates and the wedge. The splice element may further have an
extension or porch, with a ramp to facilitate insertion of the fibers into
the splice element.
A stacked splice element may be provided in the body having more than two
plates, e.g., a three-plate stack accommodating two layers of fiber
splices. Special guides positioned at each end of the plates may be used
to direct some fibers upward to one splice layer and others downward to
the other layer. End covers are provided to protect the splice element and
exposed fibers, and to provide an environmental seal.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features and scope of the invention are set forth in the appended
claims. The invention itself, however, will best be understood by
reference to the accompanying drawings, wherein:
FIG. 1 is a perspective view of the multiple optical splice device of the
present invention;
FIG. 2 is an exploded perspective view of the splice device of the present
invention;
FIG. 3 is a perspective view of the splice element used in the multiple
fiber splice device of the present invention, in its unfolded state;
FIG. 4 is an enlarged sectional perspective of one end of the splice
element of FIG. 3 showing the porch and ramp;
FIG. 5 is a sectional perspective view of the fully assembled splice device
of the present invention;
FIG. 6 is a sectional elevation of an alternative end cover used with the
splice device of the present invention, having a compartment therein for
index matching gel; and
FIG. 7 is a perspective view of the stacked splice embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference now to the figures, and in particular with reference to FIG.
1, there is depicted the multiple optical fiber splice device 10 of the
present invention. Although the term "connector" may be applied to splice
10, that term is usually reserved for devices which are intended to
provide easy connection and disconnection, as opposed to a splice which is
usually considered permanent. Nevertheless, the term "splice" should not
be construed in a limiting sense since splice 10 can indeed allow removal
of the fibers, as explained further below.
With further reference to FIG. 2, splice 10 includes a generally
rectangular body 12 which is essentially comprised of a jacket 14 and a
cap 16. Splice 10 also includes a splice element 18 and longitudinal
actuation means 20 for applying pressure to splice element 18. In the
preferred embodiment, actuation means 20 comprises a wedge 22 having
surfaces defining an acute angle, which is captured between jacket 14 and
Cap 16. A tongue 24, which is integrally molded with cap 16, is
advantageously interposed between wedge 22 and splice element 18 as
discussed further below. Jacket 14 has a longitudinal slot 26, rectangular
in Cross-section and extending through jacket 14, for receiving a splice
element 18; slot 26 is slightly shorter than splice element 18, allowing
both ends of element 18 to extend beyond the ends of slot 26. Jacket 14
also has an integrally molded male coupling element or projection 28 which
fits within a cavity 30 formed in cap 16. Projection 28 has two transverse
bumps 32 which snap into recesses 34 of cap 16, providing a snug fit
between jacket 14 and cap 16.
Jacket 14 and cap 16 each have extensions 36 and 38, respectively, which
receive end covers 40 and 42, respectively. Extensions 36 and 38 have
recessed surfaces which support the fibers at the entrance to slot 26. End
covers 40 and 42 impart protection to the spliced fibers and splice
element 18 against environmental influences. End covers 40 and 42 are
attached to extensions 36 and 38 of the jacket and cap, respectively, by
any convenient means, such as arcuate jaws 44 which snap onto and
rotatably grip trunnions 46. The side edges 48 of extensions 36 and 38 are
rounded to allow end covers 40 and 42 to rotate on trunnions 46. End
covers 40 and 42 also include hooks forming latches 50 which snap into
notches 52 in extensions 36 and 38 and securely maintain the end covers in
a tightly closed position.
Jacket 14 and Cap 16 define many overlapping surfaces which impart
additional environmental sealing and further inhibit separation of these
two components of body 12 by, e.g., bending of body 12. For example,
projection 28 has a lower tier 54 which slides under a canopy 56 formed on
cap 16. Cap 16 also includes bosses 58 which fit into recesses (not
visible in the Figures) in the corresponding face of jacket 14. Projection
28 and cap 16 further have inclined surfaces 60 and 62 which result in a
greater contact surface area and make it more difficult to pop jacket 14
and cap 16 apart by bending them near their interface.
Turning now to FIGS. 3 and 4, splice element 18 is described in further
detail. Splice element 18 may be formed from a sheet of deformable
material, preferably a malleable metal such as aluminum, although
polymeric materials may also be used. Material selection is described
further below. Certain features are embossed, coined, stamped, molded or
milled into element 18. First of all, a groove 70 is formed on the outside
surface 72 of element 18. Groove 70 forms an area of reduced thickness to
define a bend line or hinge, and separates element 18 into two legs or
plates 74 and 76 having essentially the same width. The hinge is
preferably formed by additionally embossing a notch 78, opposite groove
70, on the inside surface 80 of element. This creates a "focus hinge"
which provides more accurate registration of plates 74 and 76 when they
are folded together, as explained further below. A slot 81 may also be
punched out of element 18 to facilitate folding.
In one embodiment of the present invention, plate 76 has a series of
V-shaped grooves 82 embossed on the inside surface 80 of element 18.
V-grooves 82 are generally parallel with groove 70. Those skilled in the
art will appreciate that the V-grooves may instead be formed in plate 74,
or in both plates, and further that the shape of the grooves is not
limited to a "V" cross-section. Nevertheless, in the preferred embodiment
only one of the plates has grooves therein, and these are V-shaped having
an interior angle of about 60.degree.. In this manner, when a fiber is
placed in one of the grooves and clamped by surface 80 of plate 74, the
points of contact between element 18 and the fiber generally form an
equilateral triangle which minimizes transverse offset and thus reduces
signal loss in the splice.
Plate 74 is further distinguished from plate 76 in that plate 74 has
extensions or porches 84 which also have grooves 86 therein, although
grooves 86 do not extend the full length of plate 74. Grooves 86 are also
wider than V-grooves 82 since it is intended that the portion of the
fibers lying on porches 84 will still have their buffer coating, but this
coating is stripped from the fiber ends which are clamped between plate 74
and V-grooves 82 (i.e., the buffered portions of the fiber have a larger
diameter than the exposed portions). Grooves 86 are further recessed in
surface so, and are adjacent to ramps 88 leading up to surface so, as more
clearly seen in FIG. 4. Ramps 88 eliminate microbending (which causes
further signal loss) which would result if the buffered portion of the
fiber and the exposed portion were to lie in the same plane. In other
words, the transition from buffered fiber to exposed fiber occurs
proximate ramps 88. Accordingly, the height of ramps 88 is approximately
equal to the thickness of the buffer surrounding the fiber. Ramps 88 may
be formed in porch areas 84 although they are preferably formed in plate
74 whereby they lie under plate 76 when the plates are folded together.
As an alternative to ramps 88, recesses (not shown) may be provided in
extensions 36 and 38, under porches 84, to allow the porches to be bent
slightly downward. Such a construction would be most advantageous if the
alignment grooves on the porch of the element were continuous with the
V-grooves in the center of the element, i.e., both sets of grooves were
formed in only one of the plates forming the splice element. In this .
manner, after the fibers had been inserted and the element actuated, the
porches could be bent down to relieve bending strain on the fiber caused
by the transition in the effective diameter thereof due to the buffer
coating.
The number of V-grooves 82 and 86 in splice element 18 is variable,
depending upon the desired application. Grooves 86 should be aligned with
V-grooves 82 when splice element 18 is folded, to insure proper
positioning of the fibers during the clamping operation. Thus, while
registration of plates 74 and 76 is not as critical as with some prior art
splice devices (since there are no V-grooves on plate 74 which directly
oppose V-grooves 82) it is still beneficial to use the aforementioned
focus hinge in order to optimize the alignment of grooves 82 and 86.
In the stamping process which creates splice element 18, stop pads 90 are
also advantageously formed on both plates 74 and 76 at the corners of the
rectangle defined by the overlap of the plates. These pads are slightly
raised with respect to the otherwise flat inside surface 80 of element 18.
In this manner, when element 18 is folded as in FIG. 1, stop pads 90
provide a clearance space between plates 74 and 76, facilitating insertion
of the fibers therebetween. Alternative methods of providing such a
clearance space will become apparent to those skilled in the art. More
importantly, however, stop pads 90 insure that, when element 18 is
actuated and clamps the fibers, the maximum clamping force is exerted only
along the central width of element 18, and the clamping force gradually
decreases moving from the center toward the ends of element 18. This
gradual clamping transition has been found to significantly reduce signal
loss resulting from the deformation of the fibers, i.e., prior art splice
devices exhibited an abrupt clamping deformation which induced higher
losses.
Assembly and operation of splice 10 are both straightforward and may best
be understood with reference to FIG. 5. Splice element 18 is placed in
slot 26 in a folded state; in this state, clearance is still provided by
stop pads 90 to allow insertion of the fibers, so this may be considered
an open state, as opposed to the closed, clamping state. An index matching
gel is preferably deposited near the center of element 18 Wedge 22 is then
placed adjacent tongue 24, and jacket 14 is snapped into cap 16, whereupon
wedge 22 becomes disposed against another ramp 92 formed in the lower
portion of jacket 14. The upper surface of wedge 22 is generally parallel
with plates 74 and 76, while the lower surface of wedge 22 is parallel
with ramp 92. Tongue 24 is further supported at its distal end by a shelf
94 formed in the lower portion of jacket 14, above ramp 92. End covers 40
and 42 may be attached to extensions 36 and 38 at any time in the assembly
process (although they are not snapped into the closed position until
after the fibers have been spliced). All of the foregoing steps take place
in the factory, and splice 10 is provided to the user in the state shown
in FIG. 1 (less the fiber ribbon).
When the user has located the fibers to be spliced, they should be stripped
and cleaved according to well-known methods. In this regard, splice 10 may
be used to splice the fiber ribbons 96a and 96b shown in FIG. 1, or may be
used to splice a plurality of individual, discrete fibers. Such discrete
fibers may be more conveniently handled by first arranging them
side-by-side and applying a piece of tape or other means to effectively
create a fiber ribbon. If fiber ribbon is being spliced, the outer coating
which surrounds the individual buffered fibers should also be removed.
Once the fibers or ribbons have been inserted into body 12, splice 10 may
be actuated by longitudinally sliding wedge 22 toward jacket 14. In this
regard, the term "longitudinal" refers to movement parallel with the
fibers and grooves 82. The sliding action may be accomplished by simply
using a screwdriver or other tool to push wedge 22 forward. The
screwdriver may be applied to the cutout 98 formed in wedge 22. As wedge
22 moves forward onto ramp 92, it causes tongue 24 to press against the
outer surface of plate 74, clamping the fibers between plates 74 and 76.
The width of tongue 24 is approximately equal to the groove sets in the
plates. As discussed above, the clamping forces gradually decreases
towards the ends of splice element 18 due to stop pads 90. This effect may
be enhanced by making the lengths of wedge 22 and tongue 24 shorter than
the length of plates 74 and 76 so that the clamping force is applied
primarily at the center of splice element 18, and not at its ends. In the
preferred embodiment, the length of that portion of wedge 22 contacting
tongue 24 is about one-half the length of plate 76. The use of tongue 24
also prevents undue deformation of plate 74 which might otherwise occur if
wedge 22 were to contact splice element 18 directly. Wedge 22 provides
excellent mechanical advantages, including high transmission of forces,
and the uniform application of force parallel to plates 74 and 76. Also,
due to the coefficient of friction of the materials used for jacket 14,
wedge 22 and tongue 24, actuation means 20 (i.e., wedge 22) may be
self-locking, provided it has an angle of less than about 9.degree.. The
preferred angle is about 5.degree.. If wedge 22 is provided with a detent
or catch 99, which abuts a facing surface of cap 16, then self-locking
capability is unnecessary. Simplicity in the use of splice 10 is evident
from a summary of the above steps: stripping and cleaving the fibers,
inserting them into body 12, and sliding wedge 22 forward. A double wedge
(not shown) may be used in lieu of single wedge 22.
After the splice is completed, end covers 40 and 42 may be moved to the
closed, latched position to provide environmental sealing and protect the
exposed fibers. In this regard, legs 100 of the end covers, which rest on
stage areas 102 of porches 84, help keep the fiber ribbon aligned with
splice body 12, i.e., they oppose sideways bending of the ribbon proximate
the entrance to slot 26. Legs 100 also provide additional sealing of slot
26 since they are positioned at the sides thereof. Although not designed
for disconnection and reconnection, splice 10 may allow removal of fibers
by simply opening end covers 40 and sliding wedge 22 backward. A space 103
may be provided between jacket 14 and wedge 22, in the actuated state, to
allow insertion of a screwdriver or other tool for this purpose.
Several different materials may be used in the construction of splice 10.
Splice element 18 may be constructed from a variety of malleable metals,
such as soft aluminum. The preferred metal is an aluminum alloy
conventionally known as "3003," having a temper of 0 and a hardness on the
Brinnell scale (BHN) of between 23 and 32. Another acceptable alloy is
referred to as "1100," and has a temper of 0, H14 or H15. Acceptable
tensile strengths vary from 35 to 115 megapascals.
Other metals and alloys, or laminates thereof, may be used in the
construction of splice element 18. Such metals include copper, tin, zinc,
lead, indium, gold and alloys thereof. It may be desirable to provide a
transparent splicing element to facilitate the splicing operation. In such
a case, a clear polymeric material may be used. Suitable polymers include
polyethylene terephthalate, polyethylene terephthalate glycol, acetate,
polycarbonate, polyethersulfone, polyetheretherketone, polyetherimide,
polyvinylidene fluoride, polysulfone, and copolyesters such as Vivak (a
trademark of Sheffield Plastics, Inc., of Sheffield, Mass.).
As an alternative to providing a splice element constructed of a deformable
material, it may instead be formed of a more rigid material provided that
V-grooves 82 and/or surface so are lined with a deformable material. The
primary requisite is to provide a material which is softer than the glass
comprising the optical fiber and cladding, and which is malleable under
the clamping pressures applied to the optical fiber. It is also desirable
that the material be elastic at low stress levels to afford sufficient
elasticity to maintain a continual compressive force on the optical fibers
once plates 74 and 76 have been brought together. Furthermore, a coating
may be applied to the malleable material to reduce skiving of the material
as the fiber is inserted. For example, an obdurate coating in the range of
1 to 2 .mu.m may be applied to surface 80 of splice element 18.
Splice body 12 may also be constructed of a variety of materials, basically
any durable material and preferably one that is injection moldable,
although die cast metals are acceptable. The material should not be too
rigid as it is desirable to allow the inner walls forming slot 26 to flex
slightly to store excess clamping forces from wedge 22 in order to insure
constant clamping force on the fibers during temperature cycling.
Injection moldable materials include liquid crystal polymer, such as that
sold under the trademark VECTRA A130 by Hoechst Celanese Corp. of Summit,
N.J.
The dimensions of splice 10 may Vary widely according to the desired
application. The following (approximate) dimensions, for the preferred
embodiment, are exemplary only and should not be construed in a limiting
sense. The overall length of splice 10 is 38 mm, its height 6.7 mm and its
width 13 mm. The length of the main portion of jacket 14 is 14 mm, while
projection 28 is about 7.1 mm long and 9.7 mm wide. Cap 14 is 7.6 mm long,
and extensions 36 and 38 are each 8.3 mm long. Wedge 22 has an overall
length of 14 mm, but the length of the portion contacting tongue 24 is 10
mm. The width of wedge 22 is 6.5 mm, while its maximum thickness is 1.5 mm
and its minimum thickness is 0.76 mm.
With respect to splice element 18, several of the following approximate
dimensions are based on the size of conventional multiple fiber ribbon
cables. The length of plate 74 (including porches 84) is 28 mm, while the
length of plate 76 is 20 mm. Both plates have a thickness of 530 .mu.m,
and stop pads 90 rise 18 .mu.m above surface 80. V-grooves 82, preferably
spaced 250 .mu.m apart, are 130 .mu.m deep and have a maximum width of 180
.mu.m. Grooves 86, which are approximately trapezoidal in the preferred
embodiment, also have a maximum width of 180 .mu.m, and a minimum width of
120 .mu.m, and are 180 .mu.m deep. Ramp 88 descends 250 .mu.m, i.e., the
upper surfaces of grooves 86 are 250 .mu.m from surface 80.
Two alternative embodiments and design modifications are shown in FIGS. 6
and 7. FIG. 6 illustrates a modified end cover 42, which may be used on
both jacket extension 36 and cap extension 38. End cover 42' is used to
provide additional environmental sealing, by means of a compartment 104
defined by a wall 106 which is attached to the inner surface of cover 42,
by a living hinge 108. As end cover 42, is closed, wall 106 contacts
extension 38, causing wall 106 to compress a sealant material, which may
include index matching gel, residing in compartment 106. Wall 106 has
channels 110 therein Which allow the sealant to escape from compartment
104, and flow in and around the entrance to slot 26. A web 112 is
preferably integrally formed with wall 106, extending into compartment
104, which assures that sealant will be directed out of channels 110 when
cover 42' is closed, and also provides resistance against such closure to
prevent accidental leakage of the sealant.
FIG. 7 depicts a stacked splice device 10' which utilizes a splice element
18' having two layers of splices. Stacked splice element 18' may be formed
of three separate elements, but it is preferably constructed of a single
element having two integral hinges, folded into a Z-shape
(accordion-fold). In this manner, the three sections of the sheet defined
by the hinges result in three different plates 114, 115 and 116. It is not
necessary that the two splice layers formed thereby be parallel, but this
is preferred to simplify the wedge actuation. An alternative construction
would provide a single sheet of material having two parallel hinges
separated by a small distance, e.g., 50 .mu.m, forming the upper and lower
plates, with a third plate inserted therebetween. A plug 118 having two
sets of orifices 124 is advantageously used to guide a first set of
fibers, i.e., every other fiber, upwards to the top splice layer, and the
remaining fibers downwards to the bottom splice layer. Guide plug 118 has
grooves 120 formed in a porch area 122 thereof, similar to porch 84 of
element 18; grooves 120 help align the fibers with orifices 124. Of
course, the use of an accordion fold and guide plug could be expanded to
splice elements having more than two splice layers.
Although the invention has been described with reference to specific
embodiments, this description is not meant to be construed in a limiting
sense. Various modifications of the disclosed embodiment, as well as
alternative embodiments of the invention, will become apparent to persons
skilled in the art upon reference to the description of the invention. For
example, a multiple fiber splice device may be constructed to allow
separate termination of each fiber set by providing two actuation wedges,
one at each end of splice body 12; this would allow the pretermination of
one fiber set in the clamped state. It is therefore contemplated that such
modifications can be made without departing from the spirit or scope of
the present invention as defined in the appended claims.
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